Need a answer for all of them

Bring the fraction a/a-4 to a denominator of 16-a^2

Rationalize the denominator- 12x/√x-10

Atruck can be rented from company a $50 a day plus $0.60 per mile. company b charges $20 a day plus $0.80 per mile to rent the same truck. find the number of miles in a day at which the rental costs for company a and company b are the same